Electronic cameras usually require some type of viewfinder to preview a scene before image capture, and sometimes to review the captured image. The viewfinder typically provides a moving, or video-type, image. Because the video requirements are similar, electronic motion cameras typically use the same sensor for previewing an image, as for capturing the image. This leads to a relatively simple optical and image processing system. Electronic still cameras, particularly high resolution digital cameras, typically use an optical viewfinder for previewing an image because the imaging requirements are quite different. More specifically, the high resolution image is not immediately compatible with the video image required by the viewfinder.
Adding a zooming lens to a motion camera is a relatively simple matter, because the single optical zoom component equally affects the preview image and the captured image. However, a high resolution digital still camera with a zooming lens may become quite complex when a zooming viewfinder is required. Either an additional zoom mechanism is required for the optical viewfinder (unless the camera is a single lens reflex camera), or complicated algorithms have to be devised to extract the image in video-compatible format from the high resolution sensor at a high data rate.
Moreover, in addition to the viewfinder, a still camera requires accurate scene measurement over the actual capture field for both exposure and illuminant detection. This may also mean further components.
Consequently, it would be desirable to have a high resolution digital still camera that provides high resolution zooming of the primary image, while at the same time providing simple and cost effective zooming of the viewfinder image.